Introduce the pipeline as input → process → output, and the engine as an algorithm — a recipe followed exactly, with no judgment calls. New precision for this age: words become numbered tokens (Station II shows each word's catalogue number); the machine's memory rack holds only 24 of them — its context window — so old words fall off and are forgotten; and the output loops back into the input (Station VIII), which is why it writes one word at a time. The phone-keyboard autocomplete comparison works here: same idea, smaller machine.
The gauges are now read as percentages that sum to 100: a probability distribution, though you needn't use the phrase yet. The big idea is weighted chance: the lottery drum gives every candidate a slice of the wheel proportional to its gauge. Run the same prompt several times: different answers from identical starting conditions, because a fair draw was made from the same odds. The boiler lever makes this quantitative: cold sharpens the odds toward the favourite (repetitive), hot flattens them (surprising). This is a genuine variability-and-distributions lesson with a brass interface.
Fill in the real machines. The Difference Engine (designed from the 1820s) had one job: compute and print mathematical tables without human error — a serious matter when ships navigated by printed numbers. The government funded it lavishly but it was never completed. The Analytical Engine (from 1834) was a leap forward: a general machine with a Mill that calculates and a Store that remembers — recognisably a CPU and memory — programmed by punched cards borrowed from the Jacquard loom, which wove silk pictures from thousands of cards. Ada Lovelace translated a paper about the engine and tripled its length with her own Notes, including a card-by-card procedure for computing a famous number sequence — often called the first published computer program. In 1991 London's Science Museum finished a Difference Engine from Babbage's drawings: it weighs five tonnes, has thousands of parts, and calculates flawlessly.
Now put her claim under mild pressure: the engine just drew a word that surprised the whole class. Is surprising us the same as originating something? Where did the surprise actually come from: the machine, the “dice” (temperature), or the 79 sentences it read? Debate in pairs; there are good answers on both sides, and students should discover that "it's just following orders" and "it surprised me" can both be true at once.
Devised by Messrs. Horrocks & Claude · Oldham, Lancs. · © MMXXVI